Oklahoma was the first state forbidding people to publicly hide behind hoods and masks.
Explanation:
Governor Walton of Oklahoma dedicated himself to eliminating the Ku Klux Klan from his state in the years following WWI. However, his methods were considered extreme and controversial by many. This led to his impeachment on 1922. However, the publicity campaign that he had initiated showed everyone how dangerous and hateful the Klan could be. This led to the passage of a law that forbade people from publicly hiding behind masks or hoods. This made Oklahoma the first state to "unmask" the Klan.